Examples of a conventional heat dissipation structure that conducts heat generated in an electronic component mounted on a printed circuit board away from the electronic component include a heat dissipation structure in which a heat dissipation fin is arranged on an electronic component. Moreover, the heat dissipation efficiency is improved by interposing a heat conductive sheet between the electronic component and the heat dissipation fin. Moreover, screw boss portions are formed on the heat dissipation fin, and the heat dissipation fin and the printed circuit board are fastened together with screws, whereby the heat conductive sheet and the heat dissipation fin are fixed to the printed circuit board.
In such a heat dissipation structure, even if the dimension between the heat transfer surface of the heat dissipation fin and the printed circuit board is varied to a maximum tolerance due to the manufacturing errors of each component, it is necessary to suppress separation of the close contact surfaces between the components and the occurrence of an insufficient compressive load. Moreover, even if the dimension between the heat transfer surface of the heat dissipation fin and the printed circuit board is varied to a minimum tolerance, it is necessary to suppress the strain and deflection of the printed circuit board such that the printed circuit board is not damaged.
Therefore, a thick heat conductive sheet is used from the beginning so that the heat conductive sheet can be deformed in accordance with a change in the distance between the heat transfer surface of the heat dissipation fin and the printed circuit board. However, if the thickness of the heat conductive sheet is increased, the heat resistance increases. Thus, there is a problem in that a sufficient heat dissipation performance cannot be obtained. Moreover, there is a problem in that an increase in the thickness of the heat conductive sheet inhibits size reduction of the product.
Consequently, for example, Patent Literature 1 discloses a fixing unit that can fix both components by causing an elastic spring to be locked by a hook-shaped component mounted on the printed circuit board. With this fixing unit, even if the distance between the heat transfer surface of the heat dissipation fin and the printed circuit board changes, a contact force can be applied between the heat dissipation fin and the heat conductive sheet by the spring. Therefore, it is possible to suppress separation of the close contact surfaces between the components and the occurrence of an insufficient compressive load.